The invention is directed to an apparatus for conditioning bioinjurious waste, particularly radioactive waste, such as solutions, slimes or suspensions by compulsory mixing of the pumpable waste with a binder in a final storage container by means of a disposable stirrer permanently installed in the container.
It is known to convert radioactive wastes into a solid form suitable for final storage by mixing with suitable binders, preferably cement.
A particularly good thorough mixing can be attained in intensive mixers from which the active cement pulp is drawn off into drums. The disadvantage of this principle of mixing is the drawing off process up to the final storage container. It is also known to place the dry cement directly in the final storage container, to pump in or suck in the waste and to undertake the thorough mixing in the final storage container. This method of mixing cannot be accomplished with a simple stirring process because of the high stirring power needed on the one hand and the need for homogeneous thorough mixing on the other. To overcome these difficulties there have been proposed various solutions.
In one solution to the problem the thorough mixing takes place zonally with a planet mixer through which the stirring zone changes over the entire circumference of the container. A disadvantage of this mixing principle is the possible carrying along of contamination because the total surface of the container must remain free and in the withdrawal from the container active cement pulp adheres to the stirrer. Therefore additional precautions are necessary, namely the exact adjustment of the container rim to a hot cell lying above it and the separate cleaning of the stirrer at specific intervals.
As another solution there was proposed in German OS No. 2720342 to transfer to the final storage container through suitable installations the function of a mixing drum. A disadvantage to this proposal is the need to convey the radioactive waste through a revolving turret. Furthermore in this principle of mixing there must remain a substantial amount of free space in order to continue to guarantee the homogeneity of the final mixture. Furthermore, there cannot be employed any standard containers.
With a simple, permanently installed, uniaxial stirrer which is supported and centered at the bottom of the container, evaporator concentrates and filter sludges particularly are not homogeneously cemented, since because of the deficient mixing in the region of the stirrer axis clumps form which turn with the stirrer and do not become dissolved.
Therefore it was the problem of the present invention to develop an apparatus for conditioning bioinjurious waste, particularly radioactive waste, by forced mixing of the pumpable waste with a binder in a final storage container by means of a permanently installed disposable stirrer device which safely avoids the disadvantages of the previous practice for conditioning bioinjurious waste. The mixing process should take place in known manner with a disposable stirrer in order to present a spreading of the contamination. A homogeneous final mixing and the lowest possible stirring force should be guaranteed by a suitably shaped stirrer. In order to attain high throughput the dosaging of the waste should take place in the shortest possible time and in one step. By adjusting the stirrer geometry to the container, all standard containers should be able to be employed.